6 month old price!

Sale 1:

Sold for Bubbling Sultan's Ceremonial* (10) + 2 keys = 12 keys

http://www.tf2outpost.com/trade/27905016

http://backpack.tf/profiles/76561198124220885/#!/compare/1458630000/1459209600

http://backpack.tf/profiles/76561198063017465/#!/compare/1458777600/1458950400

Sale 2:

Involved in a bulk deal for Knifestorm Bonk Boy

[no outpost trade]

http://backpack.tf/profiles/76561198092673085/#!/compare/1458025200/1458284400

http://backpack.tf/profiles/76561198014113357/#!/compare/1458198000/1458284400

Sale 3:

Involved in a bulk deal for Sunbeams Cotton Head

http://www.tf2outpost.com/trade/27972094 | http://www.tf2outpost.com/trade/28062806

http://backpack.tf/profiles/76561198014113357/#!/compare/1459987200/1460332800

Sale 4:

Involved in a bulk deal for Scorching Coldsnap cap

http://www.tf2outpost.com/trade/28046086

http://backpack.tf/profiles/76561198043598087/#!/compare/1460246400/1460332800

Sale 5:

Sold for SCM funds

http://www.tf2outpost.com/trade/28063724

http://imgur.com/a/xAkJo

Seller received:

30.02/2.49 = ~12.06 (rounding to 12 keys)

Buyer paid:

30.02*1.15/2.49 = ~13.86 (rounding to 14 keys)

Mini-suggestion for Bubbling Sultan's Ceremonial*:

http://backpack.tf/vote/id/5709153683de6b621f030568 (credits to Blaze.xTH3RM4Lx)

~ Taking a value of 10 keys

Conclusion:

Three valid sales at 12, 12, and 14 keys. Taking a final range of 12-14 keys.

Feel free to support/counter my suggestion!